1 Technical Field
The present disclosure relates to an apparatus for driving a robot and driving method thereof, more particularly, the present disclosure relates to an apparatus for driving a SCARA robot and driving method thereof.
2. Description of Related Art
Conventional SCARA (Selective Compliance Articulated Robot Arm) robot performs a rotational displacement on a horizontal plane by a horizontal rotating arm disposed on a base, or by multiple-linked horizontal rotating arms disposed on the base so as to perform more complicated actions. A vertical working axis is usually attached to an end of the horizontal rotating arm of the aforementioned SCARA robot, and the vertical working axis usually conducts a vertical raising/lowering action and a rotating action.
The working axis is complicated in design and structure. The most common working axis in the market includes two motors, a linear way, a ball screw and a ball spline, all of which are disposed on the end of the horizontal rotating arm. One of the motors is used for driving the ball screw for performing the raising/lowering action, and the other motor is used for rotating the ball spline. Therefore, the working axis is capable of performing the raising/lowering action and the rotating motion. However, there exist some problems in the design of the working axis:
a. High cost results from the complicated structures of the two motors and the linear way.
b. The heavy weight of the two motors and the linear way cause a larger loading of the horizontal rotating arm of the SCARA robot, and therefore the increased inertia reduces the stability of the horizontal rotating arm.
c. Conventionally one of the motors is used for driving the ball screw for the raising/lowering action, and the other motor is used for rotating the ball spline; the controllability of the hardware of the two motors cooperated with other equipment and the software used for driving the motors are very complicated, which lead to a high cost on the maintenance and repairing of the machine.
There is a second kind of working axis capable of performing the raising/lowering action as well as the rotating action. In the second design, a ball screw groove and a ball spline groove are formed on the working axis, and two motors are utilized for driving the ball screw nut and the ball spline nut on the working axis. Therefore, the raising/lowering action and the rotation action can be performed by the working axis. However, the second design still has some issues as follows:
a. It is complicated and difficult to form the ball screw groove and the ball spline groove on the working axis, such that the complicated manufacturing process increases the cost.
b. The heavy weight of the two motors still makes a large burden on the horizontal rotating arm of the SCARA robot, and thus the increased inertia reduces the stability of the horizontal rotating arm.
c. It is complicated for the assembly of the ball screw groove and the ball spline groove on the working axis cooperated with the motor-driven ball screw nut and the ball spline nut, so are the controllability of the hardware of the two motors cooperated with other equipment and the software used for driving the motors. Therefore, it is difficult to reduce the cost of the assembling, maintenance and repairing of the machine.
The conventional first working axis includes motors, motor driver, linear way, ball screw, and ball spline. The second working axis utilizes a ball screw groove and a ball spline groove, servo motors and servo motor driver. Concerning the cost, the cost of the first is two or more times of that of the second. Nowadays, the SCARA robot is to increasingly important on an automated factory, so that a high cost and complicated SCARA robot but with low stability is no longer meeting demands of the industry. Therefore, a new SCARA robot structure and driving method thereof is required in the industry.